This application claims priority under 35 U.S.C. xc2xa7xc2xa7 119 and/or 365 to Korean Application No. 00-363 filed Jan. 5, 2000; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a method of forming a micro structure having nano-sized surface features.
2. Description of the Related Art
Forming a micro structure requires precise fabrication technologies since the micro structure includes a plurality of miniaturized electronic components. Generally, a thin film is grown and formed on one substrate and physicochemically cut in a predetermined pattern at a specific step to obtain a micro structure having a desired structure. In some cases, a micro structure is formed by growing and forming thin films on two substrates, cutting them in predetermined patterns, and combining the two substrates into one.
Typically, a patterning process such as photolithography or plasma etching is applied to form a regularly-structured micro structure. Sometimes a micro structure having an irregular shape with a nano- or micro-sized features may be required. However, since conventional etching techniques are chiefly applied to regularly-shaped micro structures, it is difficult to obtain micro structure having an irregular shape with a nano- or micro-sized features.
For example, it is known that a micro tip having more edges, which is an electron emission source of a field emission display, is advantageous in electron emission over that a micro chip having a single electron emission edge, but effective fabrication techniques therefor has been not yet proposed.
Micro structures other than the micro tip may also require a structure having an irregular shape of a micro scale or a nano scale.
To solve the above problems, it is an objective of the present invention to provide a method of forming a micro structure having surface roughness due to nano-sized surface features.
Accordingly, to achieve the above objective, the present invention provides a method of forming a micro structure having surface roughness due to nano-sized surface features. The method includes the steps of forming a micro structure having predetermined size and shape on a substrate; coating a carbon polymer layer on the substrate including the micro structure to a predetermined thickness; performing a first etch on the carbon polymer layer by means of plasma etching using a reactive gas in which O2 gas for etching the carbon polymer layer and a gas for etching the micro structure are mixed and forming a mask layer by the residual carbon polymer layer on the surface of the micro structure, and performing a second etch by means of plasma etching using the mixed reactive gas to remove the mask layer and etch the surface of the micro structure not covered by the mask layer so that the micro structure has nano-sized surface features.
Preferably, the carbon polymer layer is formed of polyimide or photoresist, and etched using reactive ion etching (RIE).
When etching the carbon polymer layer, the reactive gas is preferably composed of O2 as a main component and at least one of fluorine-family gases such as CF4, SF6 and CHF3 or composed of O2 as a main component and at least one of chlorine-family gases such as Cl2 and CCl4. In particular, if the reactive gas contains fluorine-family gas, at least one of CF4/O2, SF6/O2, CHF3/O2, CF4/SF6/O2, CF4/CHF3/O2, and SF6/CHF3/O2 is preferably applied. If the reactive gas contains chlorine-family gas, at least one of Cl2/O2, CCl4/O2, and Cl2/CCl4/O2 is applied.
In etching the micro structure, an etch rate is preferably adjusted by at least one of plasma power, the O2 content of the reactive gas with respect to the etch gas for etching the micro structure and a plasma process pressure, thereby controlling the surface roughness of the micro structure.